The context is e.g. the Hub transport network, shown in FIG. 1, Where several Customer Boxes CB1 . . . CBn (owned by the same customer or by different customers) have to be interconnected with a Central Site/Pop CSP via an Ethernet interface. The Central site/PoP CSP is the Hub of the data traffic among Data Boxes (not shown in FIG. 1) which can be either Routers or LAN Switches.
In order to guarantee the connectivity required by the Data Boxes, the transport network TN has to assume a Hub logical topology, in which the Customer Boxes CB1 . . . CBn connect through respective leaves LF1 . . . LFn to a Transport Network Hub TNH, in turn connected to CSP. The Transport Network transmission layer may be SDH, SONET, or ODU (Optical Layer as defined in the Recommendation ITU-T G709).
The technical problem to be solved in this context is to protect the connection between the Central Site/Pop CSP and the Transport network Hub TNH.
For protection purpose it is known to use the so-called Dual Homing Interconnection protection and/or the Equipment Protection Switching (EPS) techniques.
However in case of Hub transport network topology, there is no known way to assure the Dual Homing interconnection that is able to deal with standard external Data Boxes. It is not possible to rely on proprietary signaling because this is not supported by external Data boxes.
As far as the known EPS mechanism is concerned, usually there is an “Active” board really working by receiving and sending traffic and a “Standby” board that is not working in the sense to receive and transmit traffic, as it works only for protection of the “Active” board. Typically the “Active board” is connected to the Switching Matrix of the Transport network, while “Standby” board is disconnected from the Switching Matrix. All traffic is received/transmitted by the “Active” board and no traffic is received/transmitted by the “Standby” board. When a board failure occurs, “Active” and “Standby” roles are exchanged, and the former “Active” board becomes “Standby” and the former “Standby” board becomes “Active”. The Switching Matrix will reroute traffic from one board to the other.
This traditional EPS protection however does not work for our purpose, as the Ethernet physical layer at the level of Central Site/Pop CSP is not able to detect mono-directional failures in link TX side (up-down direction from CSP to TNH) and consequently is not able to trigger the EPS mechanism.
The result is that there is no protection in case of a mono-directional failure.